Transmission systems of this kind having a double clutch mechanism are known from the existing art.
A distinction is made in particular between two double clutch mechanism designs: on the one hand so-called double “dry” clutch mechanisms, and on the other hand so-called double “wet” clutch mechanisms.
The present invention relates more particularly to a double wet clutch.
In the case of a double wet clutch mechanism, the clutches are generally of the multiple-disc type and the friction linings of the discs are kept constantly wet with oil.
A double clutch mechanism has a first clutch, arranged for example on the gearbox side, that serves both for starting and for engagement of the odd-numbered ratios, and a second clutch, arranged for example on the engine side, that handles the even-numbered ratios and the reverse gear.
The first clutch and the second clutch alternatively transmit input power (torque and speed) from the driving shaft, which is rotationally connected to the engine, to one of the two driven shafts that are connected to the gearbox and are generally coaxial.
For improved safety, the first clutch and the second clutch of the mechanism are respectively disengaged when at rest, i.e. are “normally open,” and are actively closed by hydraulic actuating means of a control device that is associated with the double clutch mechanism.
The increasing attention being paid to double clutch mechanisms has to do in particular with the convenience and performance obtained, as well as continuous acceleration during gear changes with no interruption in torque.
Transmission systems having such a double clutch mechanism also provide a benefit in terms of consumption and CO2 emission, especially as compared with a traditional automatic gearbox.
Known transmission systems having a double wet clutch mechanism are nevertheless not entirely satisfactory, especially for certain applications.
In certain applications, especially but not exclusively for industrial vehicles such as trucks and utility vehicles, what is desired is reliable transmission of large torques with a transmission system that is still radially compact, for example in order to allow installation between the engine and gearbox of the vehicle.
The engine torque to be transmitted by transmission systems has been steadily growing for several years, reaching values on the order of 4000 Nm. Known architectures for transmission systems having a double wet clutch mechanism do not allow these torque values to be transmitted and/or do not offer satisfactory reliability.